Mauricio Santillana April 28, 2005

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Mauricio Santillana April 28, 2005
Impact of urbanization on the recharge of the
aquifer system in the Mexico City basin.

• CE 394 K2

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Outline

• Motivation.
• Long term objective.
• In class project objective.
• Description of a land development model for the
  outskirts of Mexico City.
• Coupling of a land development model with a
  hydrological model.
• Observed tendencies

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1. Motivation

• Disordered and non-regulated urban growth in
  Mexico City represents a major problem that has
  led to degradation of both, natural and social
  environments.
• Water aquifer recharge has been blocked.
• Natural reserves have been urbanized.
• High risk flooding regions are commonly
  populated.
• These problems have become a major concern in
  recent years.

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2. Long term objective
To couple an urban development model with a
simple yearly model of the aquifer system in the
south of Mexico City.
3. In class project objectives
To find tendencies in water table changes in the
aquifer with respect to urbanization using data
acquired from monitoring wells in the Mexico City.
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4. The urban development model

• The following model was designed to provide
  decision-making agencies with a suitable tool to
  generate probable scenarios of urban development
  based on a given set of hypothetical conditions.

• The mathematical framework used to simulate this
  phenomenon emanates from the study of complex and
  self-organizing systems. The model is based on
  Cellular Automata.

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4. The urban development model
The main attributes considered in the simulation
are

• Closeness to road network (Connectivity)
• Slope, topographic accidents.
• Closeness to other human settlements.
• Land Use (Rural, Forest)

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4. The urban development model
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4. The urban development modelProbable scenario
generation
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5. Coupling of a land development model with a
hydrological model.
New variable to be modeled Infiltration and
eventually recharge
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5. Coupling of a land development model with a
hydrological model.

• Once the urban model is calibrated, then the
  output is used as a dynamic input grid in a
  hydrological model where the relevant state
  variable is the infiltration.
• This qualitative approach will allow specialists
  to evaluate their hypothesis about the
  environmental impact of urbanization

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6. Identified TendenciesWater table
measurementsfrom Kriging-Interpolated grids
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6. Hypothesis

• The volume of water in the aquifer is directly
  proportional to the recharge (proportional to
  infiltration) which is inversely proportional to
  the impervious terrain (proportional to land
  development) in the recharge regions (??).

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Limitations

• Information in water resources in Mexico is
  limited and in many cases inexistent.
• Estimations of runoff, evapotranspiration,
  rainfall, infiltration, water extraction, water
  consumption per capita, are being calculated.
• A clear overexploitation of the groundwater in
  the city is taking place.

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Thank you!Comments and Observationsmauricio_at_ic
es.utexas.edu
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The model(Cellular Automata)
In order to build a suitable model, we first
divide the domain of work in grid cells. These
could correspond to pixels or sets of them, just
like in a raster image.
Each cell is in a state that depends on the
information obtained from aerial photos and
possesses attributes depending on its location.
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Cellular Automata(States and transition rules)
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4. The urban model (Results)
Real Scenario 1995
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4. The urban model (Results)
Real Scenario 2002
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4. The urban model (Results)
Output from Model 2002